Orthodontic biassing device

ABSTRACT

An orthodontic biassing device includes two spaced orthodontic expansion or contraction elements, each suitable for engaging one or more teeth. An elongated biassing assembly extends between the elements, the biassing assembly having an adjustably variable length and a body housing at each end portion thereof which is adapted to be non-rotatably and removably connected to a respective element. Preferably, the body housings are selectively connectable and removable from their respective element by relative movement therebetween in substantially only one plane. Further, the body housings are preferably non-frictionally interconnected with their respective elements. Covers are provided for enclosing the structure, the covers being selectively removable to allow for removal of a body housing from an element.

1*Nov. 25, 1975 I ORTHODONTIC BIASSING DEVICE Melvin Wallshein, 8645 Bay Parkway, Brooklyn, NY. 11214 [76] Inventor:

[ Notice: The portion of the term of this patent subsequent to Sept. 3, 1991, has been disclaimed.

[22] Filed: Dec. 23, 1974 [21] Appl. No.: 535,688

641,139 8/1950 United Kingdom 32/14 E Primary Exami er-Hugh R. Chamblee Assistant ExaminerJ. Q. Lever.

Attorney, Agent, or Firm-Flynn & Frishauf [57] ABSTRACT An orthodontic biassing device includes two spaced orthodontic expansion or contraction elements, each suitable for engaging one or more teeth. An elongated biassing assembly extends between the elements, the biassing assembly having an adjustably variable length and a body housing at each end portion thereof which is adapted to be non-rotatably and removably connected to a respective element. Preferably, the body housings are selectively connectable and removable from their respective element by relative movement therebetween in substantially only one plane. Further, the body housings are preferably non-frictionally interconnected with their respective elements. Covers are provided for enclosing the structure, the covers being selectively removable to allow for removal of a body housing from an element.

36 Claims, 15 Drawing Figures US. Patent Nov. 25, 1975 Sheet 1 on 3,921,294

U.S. Patent Nov. 25, 1975 Sheet 2 of2 3,921,294

ORTHODONTIC BIASSING DEVICE BACKGROUND OF THE INVENTION The present invention relates to orthodontic devices, and more particularly to orthodontic biassing devices which include an aperture in each one of two spaced elements, the apertures being adapted to interchangeably receive the body housings of a bias applying element.

The present invention is directed to improvements on the devices according to U.S. Pat. No. 3,832,778, issued to Melvin Wallshein on Sept. 3, 1974.

The main object of the present invention is to provide orthodontic biassing devices which are more easily used than the specific devices illustrated in said U.S. Pat. No. 3,832,778, and which require less manipulation by the operator in use.

SUMMARY OF THE INVENTION In accordance with the present invention, an orthodontic biassing device comprises two spaced orthodontic expansion or contraction elements, each suitable for engaging one or more teeth; an elongated biassing assembly extending between the elements, the biassing assembly having an adjustably variable length and a body housing means at each end portion thereof; and connecting means for non-rotatably and removably connecting each of said body housing means to a respective element, the body housing means being selectively connectable and detachable from their respective element by relative movement therebetween. By virtue of this configuration, biassing assemblies having different overall lengths can be interchanged.

According to a further feature of the invention, the body housing means are non-rotataby connectable to a respective element without the necessity of providing a friction-fit, positive structural means for preventing relative rotation therebetween being provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of one embodiment of the present invention, with the components on the left side being shown in a disassembled state, and the components on the right side thereof being shown assembled;

FIG. 2 is a cross-sectional view of the embodiment of FIG. 1 taken along the line 22 in FIG. 1;

FIG. 3 is a partial perspective view in the disassembled state of modification of the embodiment of FIG. 1;

FIG. 4 is a cross-sectional view of the embodiment of FIG. 3 taken along the lines 44 in FIG. 3, the crosssectional view showing the device in the assembled state;

FIG. 5 is a cross-sectional view of a modification to the embodiment of FIG. 3;

FIG. 6 is a cross-sectional view of a further modification to the embodiment of FIG. 3;

FIG. 7 is a cross-sectional view of a modification to the embodiment of FIG. 1;

FIG. 8 is a cross-sectional view of a further modification to the embodiment of FIG. 1;

FIG. 9 illustrates a still further embodiment of the present invention;

FIG. 10 illustrates another embodiment of the present invention, similar to that of FIG. 9;

FIG. 11 is a partial cross-sectional view of the embodiment of FIG. 10 taken along the lines 11-11 in FIG. 10;

FIG. 12 illustrates a further embodiment of the present invention;

FIG. 13 illustrates a still further embodiment of the present invention, similar to that of FIG. 12;

FIG. 14 is a perspective view ofa still further embodiment of the present invention; and

FIG. 15 is a side view of the embodiment of FIG. 14 showing the cover in the open and closed positions.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS The orthodontic devices of the present invention are used in much the same manner as those described in my prior U.S. Pat. No. 3,832,778, the contents of which are incorporated herein by reference. and are adapted to be either directly connected to tooth holding means via wire members extending from the orthodontic devices, or to be embedded in acrylic devices which engage respective teeth, the orthodontic devices of the present invention being utilized to vary the dis tance between the acrylic members. It is further pointed out that the expansion devices described herein can be easily adapted to operate as contraction devices within the scope of the present invention, as disclosed and claimed herein.

Referring to FIG. 1, an expansion type orthodontic device is illustrated, the left hand portion thereof being shown in an exploded disassembled view, the right hand section thereof being shown in the assembled state. FIG. 2 is a cross-sectional view along the line 22 in FIG. 1.

The device of FIG. 1 includes an expansion screw device, generally designated by the reference numeral 10, the construction of which, per se, is well known in the art. Such an expansion screw device 10 includes a pair of body housings l1, 12, each of which is provided with an internal thread which respectively meshes with oppositely threaded screw portions 13, 14 of a spindle. Positioned between the two screw portions 13, 14, is a non-threaded spindle engaging portion 15 which is provided with radial holes 16 adapted to be engaged by a special tool or simply an elongated pin which may fit into the holes so as to rotate the spindle. Rotation of the portion 15, which causes relative rotation between the screw portions l3, l4 and the body housings ll, 12, either spreads the body housings 11, 12 apart or pulls them toward each other, depending upon the direction of rotation of the spindle engaging portion 15.

The body housing 11 is insertable into an outer shell member 17, which has a metal extension 18 secured to an end thereof, for example by spot welding, the metal extension 18 being adapted to be secured to a tooth engaging structure, or the like. The metal extension 18 has a cross-bar portion 19 which extends substantially diametrically across the cylindrical shell 17 and provides a space between the bar 19 and the bottom of the shell 17 for engagement of the body housing extension 20 in said space. The body housing extension 20 has a substantially flat upper surface which matingly engages the cross-bar 19 when the body housing is fully inserted into the shell 17, thereby positively preventing rotation of the body housing 11 relative to the shell 17. The body housing extension 20 has the extreme end portion 20 thereof formed with a radius so as to facilitate insertion of the extension 20 under the cross-bar l9.

The body housing further has pins 21 extending therefrom. the pins 21 being engageable in slots 22 of shell 17. The pins 21, when engaged in slots 22, further prevent relative rotation between the body housing 11 and the shell 17. The slots 22 have wide mouth openings to facilitate insertion of the pins 21 therein. Additionally, the pins 21 prevent tilting of the body housing 11 in the counterclockwise direction relative to the shell 17 so as to counteract tilting forces which may be applied to the apparatus when used in orthodontic applications. Additionally, the body housing extension 20, in cooperation with the cross-bar l9, prevent clockwise tilting of the body housing 11 relative to the shell 17.

A cover 23 is provided for engagement with the shell 17 to cover the upper portion of the body housing and to positively retain the body housing 11 within the shell 17. The cover 23 has longitudinal protrusions 24 which respectively engage grooves 25 formed in the outer surface of the shell 17. The protrusions 24, in cooperation with the grooves 25 snappingly engage the cover to the shell and positively retain the structural components together. The right hand portion of FIG. 1 and the sectional view of FIG. 2 clearly illustrate the cooperation of the cover 23 with the shell 17 and body housing 11 The cover 23 is provided with an opening 26 in the upper portion thereof for use in removing same from the shell 17. In use. a removal tool is hooked under the edge 27 of the cover 23, and another portion of the removal tool is located within the opening 26 so as to press upon the body housing 11. In this manner, sufficient leverage is obtained so as to easily remove the cover 23. Moreover, since one portion of a removal tool will be passed through the opening 26 and pressed upon the upper portion of the body housing 11, after the cover 23 becomes loose from the shell 17, the cover 23 will be positively prevented from falling loose into the patients mouth.

The right hand portion of FIG. 1 is identical to the left hand portion thereof, except the elements are shown in an assembled state. Corresponding elements in the right and lefthand portions of FIG. 1 are given the same reference numerals, the right hand reference numerals being primed. Likewise, FIG. 2 is directed to the right hand portion of FIG. 1, and various reference numerals therein are primed.

FIG. 3 illustrates a modification of the embodiment of FIG. 1. In FIG.'3, only the left hand portion of the orthodontic device is shown, the expansion screw device and the right hand portion thereof being omitted for ease of illustration. The expansion screw device usable with the FIG. 3 embodiment is similar to that of FIG. 1. In FIG. 3, the shell 30 is shown embedded in an acrylic member 31, only a portion of the acrylic member being shown for ease of illustration. The shell 30 includes protrusions 32 on each side thereof which are embedded in the acrylic 31 so as to provide better engagement between the shell 30 and the acrylic 31, and to prevent relative rotation therebetween. A metal extension 33 is secured to an end of the shell 30, for example by spot welding. and the metal extension 33 includ'es a cross-bar portion 34, which is similar to the cross-bar portion 19 of FIG. 1. The body housing 35, which is internally threaded in the same manner as the body housing 11 of FIG. 1, has a substantially flat bottom and substantially flat sides which extend at substantially right angles to the bottom. The body housing 5 is dimensioned so as to fit within the part-rectangular 4 opening 36 in the shell 30. The body housing has an extension 37 which is adapted to fit under the cross-bar 34 in the same manner as in FIG. 1. The body housing extension 37 has a radius portion 37' so as to facilitate insertion thereof under the cross-bar 34. By virtue of the generally rectangular shape of the body housing 35 and of the opening 36 in the shell 30, the body housing is non-rotatably retained within the shell 30 in a positive and structurally secure manner. The body housing extension 37 substantially prevents tilting of the body housing 35 in a clockwise manner relative to the shell 30. Depending upon application, and if desired, pins similar to pins 21 and corresponding slots similar to slots 32 may be provided in the body housing 35 and shell 30, respectively. so as to prevent relative tilting in the opposite direction. In most applications, as seen in FIG. 3 the main tilting effect is one which causes a clockwise tilt of the body housing 35 relative to the shell 30, and the provision of the body housing extension 37 is sufficient to prevent such relative tilting between the body housing 35 and the shell 30. The lesser tilting effect in the opposite direction is obviated by the engagement of the cover.39 with the shell 30.

As seen in FIGS. 3 and 4, the upper surface 38 of the body housing 35 has a curvature which preferably matches the outer curvature of the shell 30, so that when the body housing 35 is inserted within the shell 30, the overall construction exhibits a generally circular and continuous outer contour. A cover 39 is provided which operates in a manner similar to that of cover 23 of FIG. 1. The cover 39 is provided with an opening 40 for use in disengaging the cover 39 from the shell 30. Further, the cover has longitudinal internal protrusions 41 which are engageable with respective grooves 42 in the shell 30. The cover 39 may be removed as described with respect to FIG. 1, or it may be removed by sliding same to the right in FIG. 3 since the grooves 42 extend to the edge of shell 30.

In the FIGS. 1 and 3 embodiments, the cross-bars 19 and 34, respectively, in addition to serving the function of preventing tilting of the body members relative to the shells, further serves the function of providing an endstop for the body housings engaged in the respective shells. For example, when the orthodontic device of the present invention is utilized as an expanding device, the body housings are urged outwardly by rotation of the screws 13 and 14 and are urged against the crossbars 19 and 34. Thus, the cross-bars and associated body housing extensions cooperate to provide longitudinal abutment means as well as a tilt prevention mechanism. I

FIG. 5 shows a modfied cover 43 for use with the shell 30 and body housing 35 of FIG. 3. The cover 43 of FIG. 5 is also usable with the shell 17 and body housing 11 of FIG. 1. In FIG. 5, the cover 43 is made of a spring metal, as are the covers 23 and 39 of FIGS. 1 and 3, respectively. The cover 43 is a part of cylindrical structure, which, in cross section, has a circumference greater than a semi-circle. The cover 43 of FIG. 5 is snapped over the shell 30 and acts as an over-center device relative to the shell 30. During the snappingon procedure, the cover 43 flexes so as to fit over the shell and springs back tending to return to its original shape, thereby tightlyengaging the shell 30. In the removed state, the cover 43' generally defines'a smaller diameter opening than the diameter of shell 30, thereby providing a tight and secure fit. The cover 43 preferably has an opening 44 therein so that the cover 43 is removable in the same manner as the covers 23 and 39 of FIGS. 1 and 3, respectively.

FIG. 6 illustrates a modified cover 45 which is similar to that of FIG. 5, except that the cover 45 is adapted to slide circumferentially about the shell 30 in the directions of the arrow 46. In FIG. 6, the cover is shown in the open condition. To close the cover, the cover 45 is rotated in the clockwise direction until the longitudinal protrusion 47 thereof engages a longitudinal groove 48 in the shell 30. Again, the cover 45 is fabricated of a spring metal so that tight engagement between the cover 45 and shell 30 is obtained.

FIG. 7 illustrates a modification to the embodiment of FIGS. 1 and 2. Corresponding elements in FIGS. 2 and 7 are given the same reference numerals. As seen in FIG. 7, the body housing 12 has a longitudinal protrusion 49 extending therefrom. The shell 17 has a plurality of grooves 50-54 formed therein in the longitudinal direction thereof. The plurality of grooves 5054 facilitates insertion and engagement of the body housing 12 with the shell 17 and reduces the amount of manipulation required to attain proper engagement. In the case where the body housing has an extension similar to the extension 20 of FIG. 1 which engages a crossbar 19, then it will be possible for the protrusion 49 to engage only the groove 52. However, in certain instances, the extension 20 may not be required, for example in situations where tilting of the component would not be a problem or in situations where the cover 23' will provide sufficient retention to prevent relative tilting between the body housing 12' and the shell 17. In such an instance, the plurality of grooves 5054 permits the body housing 12 to be engaged with the shell 17 in a plurality of different positions, thereby reducing the amount of manipulation necessary to achieve proper engagement of the parts.

FIG. 8 illustrates a modification similar to that of FIG. 7, except that the shell 17' has only two longitudinal grooves 55, 56 and the body housing 12' has only two longitudinal protrusions 57 and 58. In the positions shown in FIG. 8, the grooves and protrusions will nonrotatably lock the body housing 12' into the shell 17 and will additionally provide an anti-tilting effect. The anti-tilting effect in some cases may be sufficient to eliminate the need for the body housing extension 20 and/or the pins 21 and associated slots 22 of FIG. 1. The grooves and protrusions of FIG. 8 may be located further apart relative to each other about the circumference of the shell 17'. However, the further apart they are located, the more difficult it becomes to engage the protrusions with their respective grooves.

FIG. 9 illustrates a further embodiment of the present invention, only one generally rectangular shell 60 and one generally rectangular body housing 61. The body housing 61 has an internal thread for receiving an expansion screw device, similar to the orthodontic appliance of FIG. 1, and a second shell and body housing is provided on the other side of the expansion screw device, as shown in FIG. 1. The rectangular shell 60 has a rear wall 62 to which is secured, for example by welding, the metal extension 63, which is similar to the extensions 18 and 33 of FIGS. 1 and 3, respectively. The shell 60 has tabs 64 and 65 which are bendable to the position shown in FIG. 10 so as to firmly secure the body housing 61 within the shell 60. The tabs are normally in the upright position, and after insertion of the body housing 61 into the shell, by moving the body housing in the direction of the arrow 66, the tabs 64, 65

are bent over to engage the body housing 61 as shown in FIG. 10. To remove the body housing 61, the tabs 64, 65 are bent to their upright position and the body housing 61 is withdrawn in a direction opposite to the direction of arrow 66. This type of movement is necessary due to the restricted areas within the mouth and due to the fact that the expansion screw device, similar to device 10 of FIG. 1, cannot be reduced in length a sufficient amount to enable the body housing 61 to be withdrawn in the direction of the axis of the threaded screw hole therein.

A dimple 67 is provided in at least one of the walls of the shell 60 to engage a corresponding indentation 68 on the body housing 61, for example as shown in FIG. 10. The engagement of the dimple 67 with the indentation 68 retains the body housing in the shell temporarily during bending over of the tabs 64, 65 and greatly facilitates installation of the appliance in the mouth of a patient.

FIG. 11 shows an embodiment of the invention similar to that of FIG. 9, but instead of providing tab 64, 65, a snap-on cover 69 is provided. In FIGS. 9 and 11, corresponding elements are designated with the same reference numerals. As in FIG. 9, the metal extension 63 is connected to a rear wall (not seen in FIG. 11) of the shell 60. The snap-on cover 69 has bent-in ends 70, 71 so as to grip around the lower edges of the shell 60 to provide firm engagement of the cover 69 with the shell 60. The cover 69 is preferably made of a spring metal so as to facilitate its engagement and disengagement with the shell 60. Preferably, the shell 69 has an opening 72 in the upper surface thereof for insertion of a removable tool therein. As in the embodiments of FIGS. 1 and 3, the insertion of the removal tool through the hole 72 enables greater removal forces to be applied to the bent in ends 70, 71 and further provides retention of the cover 69 after it is disengaged from the shell, thereby preventing it from falling loose in the patients mouth.

FIG. 12 illustrates another embodiment of the invention which comprises an inner shell member 76 and an outer shell member 77 which is secured to the inner shell 76, for example by welding, preferably at the ends thereof as indicated by weld 78 in FIG. 12. The ends 79, 80 of the outer shell 77 are bent inwardly over the ends of the inner shell 76 so as to form inwardly extending lips. A metal extension 81 having a cross-bar portion 82 is welded to the inner shell 76, similar to the metal extensions 18 and 33 of FIGS. 1 and 3, respectively. The outer shell 77 is fabricated of a material having some give or springiness so that the inwardly extending lips 79, 80 may be sprung outwardly when outward forces are applied thereto. A generally cylindrical body housing 83 has a threaded hole therethrough, as the previously described body housings, and further has a body housing extension 84 extending therefrom which is engaged between the lower portion of the inner shell 76 and the cross-bar 82. Rather than having a radius at the leading edge'thereof, the body housing extension 84 has a flat, sloping upper surface 85 which facilitates its engagement under the cross-bar 82. The body housing 83 has grooves 86, 87 on opposed sides thereof which are dimensioned and located so as to have the inwardly extending lips 79, 80 engaged therein when the body housing 83 is fully engaged with the shell members. In order to mount the body housing 83 to the shell members, the body housing 83 is lowered in the direction of the arrow 88 into 7 the inner housing 76, the curved surface of the housing 83 causing the outer housing 77 to flex, thereby permitting the lips 79, 80 to move outwardly. When the body housing is depressed so that the grooves 86, 87 register with the lips 79, 80, respectively, the springiness of the outer shell 77 cause the lips 79, 80 to spring inwardly in engagement with the respective grooves in the body housing 83. Then. the body housing 83 is moved in the direction of the arrow 89 by a small amount so that the body housing extension 84 becomes engaged under the cross-bar 82. The movement of the body housing 83 in the direction of the arrow 89 may be accomplished manually or may be accomplished by rotating the expansion screw device so as to cause the body housing 83 to move in the direction of arrow 89. Since the shell members are fixedly secured to a tooth, or the like. rotation of the expansion screw device will cause relative movement between the body housing 83 and the shell 7 members so as to permit the body housing extension 84 to be engaged under the cross-bar 82.

In the embodiment of FIG. 12, a cover is not absolutely necessary. However, if it is desired to provide a cover to, for example. keep food or other debris out of the mechanism. then a cover similar to the cover of FIGS. 1 and 3, for example, may be provided.

FIG. 13 illustrates an embodiment of the invention similar to that of FIG. 12, except that the device of FIG. 13 may be embedded in acrylic. The body housing 83 of FIG. 13 is substantially identical with that of FIG. 12, except possibly for dimensioning. The shell structure of FIG. 13 comprises an inner shell 90 and an outer shell 91 which is secured to the inner shell, for example by welding, at a point thereon remote from the longitudinal ends of the shells. The inner shell has bent-in ends 92,93 which form lips for engagement with grooves 86,87, respectively, in the same manner as in FIG. 12. The inner shell of FIG. 13 is made ofa springy material, for example spring-type metal, so that it may flex outwardly when the body housing 83 is inserted therein and so that is may then flex inwardly when the lips 92,93 are in registration with the grooves 86,87 so as to cause positive engagement of the lips 92,93 in the grooves 86,87. The metal extension 82 is secured, for example by welding, to the outer shell member 91 in the embodiment of FIG. 13. Insertion of the body housing 83 into the shell members of FIG. 13 is accomplished in the same manner as described above with respect to FIG. 12. Again, a cover may or may not be provided, as desired, in the embodiment of FIG. 13.

FIGS. 14 and illustrate a further feature of the invention whereby a hinged type cover 94 engages extended end portions 95,96 of a metal extension 97 which is secured to a shell 98. FIGS. 14 and 15 omit the body housing for clarity of illustration. However, it should be clear that a body housing such as that shown in FIG. 1 is usuable with the device of FIGS. 14 and 15. Moreover, it should be clear that the shell 98 is shown with cylindrical inner and outer walls only by way of example the shell of FIG. 3 may also be used with the embodiments of FIGS. 14 and 15. The cover 94 has openings on opposing sides thereof for engagement with the extended portions of the metal extension 97. For ease of understanding, only one such opening 99 will be discussed. it being clear that a corresponding opening is provided on the opposing side of the cover 94 for engagement with the extended portion 95 of the metal extension 97. The opening 99 has an entrance portion 100 which is dimensioned so as to be slightly smaller than the outer diameter or outer dimension of the metal extension 97. The opening 99 has an inner portion 101 which is dimensioned so as to provide a relatively loose fit with respect to the metal extension 97. The cover 94 is mounted to the shell structure by forcing the entrance portion of opening 99 over the extended portion of the metal extension 97 until the metal extension 97 is received in the enlarged inner portion 101, as shown in FIG. 14. At this point, due to the relatively loose fit between the metal extension 97 and the inner portion of the opening 101, the cover may be easily pivoted about the extended portions 95,96 of the metal extension 97. The cover 94 is preferably provided with an end tab 102/or longitudinal projection on each side thereof which engages, for example, a/corresponding depression 103 in the outer wall of the shell 98, so as to lock the cover 94 in a closed position.

FIG. 15 is a side view of the embodiment of FIG. 14 with the cover 94 shown in the closed position by solid lines and in the open position by chain lines. The cover 94 is swingable about its pivot connetion to the metal extension 97 in the direction of the arrow 104.

The construction of FIGS. 14 and 15 is particularly advantageous in that the cover 94 may be conveniently opened without the danger of it falling loose within the patients mouth, thereby preventing danger to the patient. Moreover, the cover may be hingedly mounted to the metal extension 97 at the factory or by the operator prior to insertion of the device in the patients mouth. This eliminates the difficult task of locating the relatively small covers and engaging them with the shells within the patients mouth, as is required with with the embodiments illustrated in FIGS. 1-l1. Thus, the embodiment of FIGS. 14 and 15 improves safety and further facilitates use of the invention in actual practice. By providing the openings 99 close to the lower edge of the cover 94, the cover 94 is swingable as shown by the chain lines in FIG. 15 to a fully open position whereby it presents substantially no obstruction to the insertion and removal of the body housings from the shell in the direction perpendicular to the longitudinal axis of the shell. In FIGS. 14 and 15, various other locking arrangements can be used in place of the tabs 102 and their corresponding depressions 103.

In all of the embodiments illustrated and described herein, the critical features include mounting of the body housing within the shell so that it is non-rotatably retained in the shell, and so that it may be removed by movement in substantially a single direction which is preferably perpendicular to the longitudinal direction of the shell. The removability by movements substantially only in the direction perpendicular to the longitudinal axis of the shell (or the longitudinal axis of the expansion screw device) is extremely important to facilitate use of the device within the restricted areas of the patients mouth.

Referring to FIG. 9, a guide pin which slideably engages in a deep hole in the body housing 61 is shown. The guide pin likewise is slideably engaged in the opposed body housing at the other end of the biassing device (not shown). In practice, when an operator is installing the biassing device of the present invention, the various parts may rotate relative to each other about the axis of the device and thereby lengthen or shorten the overall device. The provision of the guide pin 1 10, which is slideably received at each end of the biassing device, prevents such relative rotation and facilitates manipulation of the device when installing same in a patients mouth.

While the Figures illustrate the device of the present invention used as an expansion device, the device may also be used as a contraction device for example by providing a cross-bar similar to the cross-bars of the Figures at the opposite end of the respective shells. These cross-bars at the opposite ends of the shells would engage respective body housings which may optionally include extensions which engage under the bars. Other end-stop means could be provided, as desired.

In the present invention, there is no necessity to provide a friction or press-fit between the body housings and the shells in which the body housings are inserted. In the embodiments of the present invention, positive, structural means provides an interference or abutment fit between the members so as to prevent relative rotation and relative tilting between the shells and the body housings inserted therein. If desired, the parts may be dimensioned so as to additionally provide a friction-fit. However, the elimination of the necessity of the friction-fit makes it easier for the operator to manipulate the various components of the present invention within the small confines of the patients mouth, thereby greatly facilitating use thereof in actual practice.

While the invention has been described above with respect to specific apparatus and embodiments, various modifications and alternations may be made thereto within the scope of the invention as defined in the appended claims. For example, the embodiments of the invention which are shown with cover members can be used as well without the cover members in many applications. Additionally, while the cover of FIG. 14 is shown hinged relatively close to its longitudinal edges, the shell member may be made higher and the crossbar may be mounted in a higher position, resulting in the hinge pivot point being located at a point higher relative to the longitudinal edge of the cover than as shown in FIG. 14. By providing the pivot point at a raised position relative to the lower edge of the cover, the cover will require less space for opening thereof. For example in FIG. 15, if the pivot point were raised relative to the longitudinal edge of the cover, the cover in its open position would not extend as far to the left as illustrated in FIG. 15. Further, the opening 101 need not be opened via the entrance portion 100. The opening 101 may be closed and the cross-bar inserted therein during construction of the device. Still further, the cover of FIG. 14 can be hinged along one of its longitudinal edges, rather than as shown in FIG. 14. Still further, while the cross-bar has been shown attached to the edges of the various shell members, the cross-bar could be recessed into the various shell members so as not to protrude from the end thereof, and the cross-bar may be located higher or lower than illustrated, depending upon application. In the case where the crossbar is recessed within the shell member, a still further reduced amount of clearance is required for opening the cover, which may be advantageous under certain conditions. Still further, as discussed above, abutment members may be provided at the ends of the shell members opposite the metal extensions to retain the body housings therein so that the devices of the present invention can be used as contraction devices. A dummy may be used in place of the body housings and screw threaded portions for use in installing the device in a patients mouth. After installation, the dummy may be 10 removed and the device then operatively assembled. In FIG. 3, when embedded in acrylic 31, the metal extension 18 may be omitted and the acrylic material or other means may serve as the end stop.

While the various embodiments are illustrated by way of example, it should be clear that various combinations of features from the various illustrated Figures could be combined, as desired, so as to provide various different structures in accordance with the present in vention as defined in the appended claims.

I claim:

1. An orthodontic biassing device comprising two spaced orthodontic expansion or contraction elements, each suitable for engaging one or more teeth; an elongate biassing assembly extending between said elements and including a body housing means at each end portion thereof, said biassing assembly having an adjustably variable length; and

connecting means for nonrotatably and removably connecting each of said body housing means to a respective element such that each of said body housing means are selectively connectable and detachable from their respective element by relative movement therebetween, whereby biassing assemblies having different overall lengths can be interchanged.

2. An orthodontic biassing device according to claim 1 wherein said connecting means non-frictionally connects each of said body housing means to a respective element.

3. An orthodontic biassing device according to claim 1 wherein said body housing means are detachable from their respective element by relative movement therebetween in substantially a single plane.

4. An orthodontic biassing device according to claim 1 wherein said elements each comprise a hollow member defining a receptacle for a respective body housing means, and wherein said connecting means comprises a first connecting member coupled to said hollow member and a second connecting member on said body housing means engaging said first connecting member for non-rotatably connecting said body housing means to a respective element.

5. An orthodontic biassing device according to claim 4 wherein said first connecting means comprises a bar extending across the hollow portion of said hollow element and said second connecting means includes an extension extending from an end of said body housing means and having a contour which corresponds to the shape of said bar, said extension engaging under said bar for non-rotatably connecting said body housing means to its respective element.

6. An orthodontic biassing device according to claim 5 wherein said connecting means further comprises at least one projection extending from said body housing means and at least one slot in said element, said projection engaging said slot for non-rotatably connecting said body housing means to its respective element.

7. An orthodontic biassing device according to claim 6 wherein said at least one projection is located at the end of said body housing means which is opposite from the end from which said extension extends, said extension preventing tilt of said body housing means relative to said element in a first direction, and said projection and slot preventing tilt of said body housing means relative to said element in the opposite direction.

8. An orthodontic biassing device according to claim 1 wherein said connecting means comprises a generally part rectangular hollow opening in said element, and a generally at least'part rectangular outer profile of said body housing means, said generally at least part rectangular profile of said body housing means being dimensioned so as to engage said opening of said element to prevent relative rotation therebetween.

9. An orthodontic biassing device according to claim 8 wherein said connecting means further comprises a bar extending across the hollow portion of said element, and an extension extending from an end of said body housing means and having a contour which corresponds to the shape of said bar, said extension engaging under said bar for non-rotatably connecting said body housing means to its respective element.

10. An orthodontic biassing device according to claim 1 wherein said connecting means comprises a projection on at least one of said element and body housing means, and a corresponding groove on the other of said element and body housing means for receiving said projection, thereby non-rotatably connecting said body housing means to its respective element.

11. An orthodontic biassing device according to claim 10 wherein each of said body housing means and elements are elongated elements, and comprising a pair of spaced projections and grooves which are respectively engageable to prevent relative rotation and relative tilting between a body housing means and its respective element.

12. An orthodontic biassing device according to claim 11 wherein both of said grooves are formed in one of the element and body housing means, and both of said projections are formed in the other of said element and body housing means.

13. An orthodontic biassing device according to claim 1 wherein said elements each comprise first and second elongated shell members, each defining an access opening in the longitudinal direction thereof, the longitudinal running ends of said shell members being displaceable relative to each other and one of said shell members having inwardly extending lip members which extend further toward the longitudinal central axis of said shell members than the end portions of the other of said shell members, and wherein said body housing means include a pair of elongated slots formed therein which are respectively engageable with said lip members of said shell member.

14. An orthodontic biassing device according to claim 13 wherein said first and second elongated shell members are located one within the other, said inner shell member comprising a hollow member, and wherein the outer elongated shell member is of a springy material and includes said inwardly extending lip members.

15. An orthodontic biassing device according to claim 14 further comprising a bar member secured to an end of said inner member and extending across said hollow opening.

16. An orthodontic biassing device according to claim 15 wherein said body housing means includes an extension extending from an end thereof and adapted to engage under said bar member.

17. An orthodontic biassing device according to claim 13 wherein said first and second elongated shell members are located one within the other, said outer shell member comprising a hollow member, and wherein said inner shell member is of a springy material 12 which defines a hollow opening, said inner shell member including said inwardly extending lip members.

18. An orthodontic biassing device according to claim 17 further comprising a bar member secured to an end of said outer member and extending across said hollow opening.

19. An orthodontic biassing device according to claim 18 wherein said body housing means includes an extension extending from an end thereof and adapted to engage under said bar member.

20. An orthodontic biassing device according to claim 17 wherein said outer shell member is embedded in acrylic, or the like.

21. An orthodontic biassing device according to claim 1 comprising a bar member extending across an end of each of said elements, said bar member serving as an end stop for said body housing means inserted in said elements.

22. An orthodontic biassing device according to claim 1 wherein said connecting means comprises at least one projection extending from said body housing means and at least one slot in said element, said projection engaging said slot for non-rotatably connecting said body housing means to its respective element.

23. An orthodontic biassing device according to claim 1 wherein each of said elements includes a hollow member for receiving a body housing means and an openable cover coupled to said hollow member to provide an access opening for connecting and detaching a body housing means from its respective element.

24. An orthodontic biassing device according to claim 23 wherein said cover includes a projection thereon and wherein said hollow member includes a groove therein which is adapted to receive said projection for locking said cover to said hollow member.

25. An orthodontic biassing device according to claim 23 wherein said hollow member comprises a generally part-cylindrical member, and wherein said cover comprises a generally part-cylindrical member which is engageable with said hollow element to form a generally cylindrical member when said cover is closed.

26. An orthodontic biassing device according to claim 23 wherein said cover has an opening therein so as to allow communication with a body housing means through said cover when said cover is closed.

27. An orthodontic biassing device according to claim 25 wherein said cover is formed of a springy material and has at least one projection thereon, and wherein said hollow member includes a depression therein which is adapted to receive said at least one projection for locking said cover to-said hollow member in the closed position.

28. An orthodontic biassing device according to claim 23 wherein said cover is hingedly coupled to said hollow element.

29. An orthodontic biassing device according to claim 28 wherein said hollow member includes means extending therefrom in the vicinity of an end thereof, and wherein said cover includes an opening engageable with said extending means for hingedly coupling said cover to said hollow member.

30. An orthodontic biassing device according to claim 29 wherein said opening comprises a first entrance portion having a width which is smaller in dimension than the thickness of said projection, and a second opening portion interior of said entrance portion and which is dimensioned so as to loosely receive said projection.

31. An orthodontic biassing device according to claim 23 wherein said hollow member is a generally part-cylindrical member and wherein said cover comprises a generally part-cylindrical member formed of a springy material and which comprises more than half a cylinder in cross-section, said cover being slideable about the periphery of said hollow member for selectively opening and closing said access opening.

32. An orthodontic biassing device according to claim 31 wherein said cover has a projection thereon and wherein said hollow member includes a depression therein which is adapted to receive said projection for locking said cover to said hollow member in the closed state.

33. An orthodontic biassing device according to claim 1 wherein each of said elements includes a hollow member including an access opening for receiving a body housing means, and tab means extending from said hollow member which are foldable over an in- 14 serted body housing means for locking said body housing means into said hollow member.

34. An orthodontic biassing device according to claim 33 wherein at least one of said hollow member and body housing means has a projection thereon, and wherein the other of said hollow member and body housing means has a depression therein engageable with said projection for locking said body housing means in said hollow member.

35. An orthodontic biassing device according to claim 23 wherein said hollow member is generally rectangular, and wherein said cover includes means extending over a substantial portion of said hollow member and engageable with at least one edge of said generally rectangular hollow member.

36. An orthodontic biassing device according to claim 23 wherein said cover has a through opening therein communicating with said body housing. 

1. An orthodontic biassing device comprising: two spaced orthodontic expansion or contraction elements, each suitable for engaging one or more teeth; an elongate biassing assembly extending between said elements and including a body housing means at each end portion thereof, said biassing assembly having an adjustably variable length; and connecting means for non-rotatably and removably connecting each of said body housing means to a respective element such that each of said body housing means are selectively connectable and detachable from their respective element by relative movement therebetween, whereby biassing assemblies having different overall lengths can be interchanged.
 2. An orthodontic biassing device according to claim 1 wherein said connecting means non-frictionally connects each of said body housing means to a respective element.
 3. An orthodontic biassing device according to claim 1 wherein said body housing means are detachable from their respective element by relative movement therebetween in substantially a single plane.
 4. An orthodontic biassing device according to claim 1 wherein said elements each comprise a hollow member defining a receptacle for a respective body housing means, and wherein said connecting means comprises a first connecting member coupled to said hollow member and a second connecting member on said body housing means engaging said first connecting member for non-rotatably connecting said body housing means to a respective element.
 5. An orthodontic biassing device according to claim 4 wherein said first connecting means comprises a bar extending across the hollow portion of said hollow element and said second connecting means includes an extension extending from an end of said body housing means and having a contour which corresponds to the shape of said bar, said extension engaging under said bar for non-rotatably connecting said body housing means to its respective element.
 6. An orthodontic biassing device according to claim 5 wherein said connecting means further comprises at least one projection extending from said body housing means and at least one slot in said element, said projeCtion engaging said slot for non-rotatably connecting said body housing means to its respective element.
 7. An orthodontic biassing device according to claim 6 wherein said at least one projection is located at the end of said body housing means which is opposite from the end from which said extension extends, said extension preventing tilt of said body housing means relative to said element in a first direction, and said projection and slot preventing tilt of said body housing means relative to said element in the opposite direction.
 8. An orthodontic biassing device according to claim 1 wherein said connecting means comprises a generally part rectangular hollow opening in said element, and a generally at least part rectangular outer profile of said body housing means, said generally at least part rectangular profile of said body housing means being dimensioned so as to engage said opening of said element to prevent relative rotation therebetween.
 9. An orthodontic biassing device according to claim 8 wherein said connecting means further comprises a bar extending across the hollow portion of said element, and an extension extending from an end of said body housing means and having a contour which corresponds to the shape of said bar, said extension engaging under said bar for non-rotatably connecting said body housing means to its respective element.
 10. An orthodontic biassing device according to claim 1 wherein said connecting means comprises a projection on at least one of said element and body housing means, and a corresponding groove on the other of said element and body housing means for receiving said projection, thereby non-rotatably connecting said body housing means to its respective element.
 11. An orthodontic biassing device according to claim 10 wherein each of said body housing means and elements are elongated elements, and comprising a pair of spaced projections and grooves which are respectively engageable to prevent relative rotation and relative tilting between a body housing means and its respective element.
 12. An orthodontic biassing device according to claim 11 wherein both of said grooves are formed in one of the element and body housing means, and both of said projections are formed in the other of said element and body housing means.
 13. An orthodontic biassing device according to claim 1 wherein said elements each comprise first and second elongated shell members, each defining an access opening in the longitudinal direction thereof, the longitudinal running ends of said shell members being displaceable relative to each other and one of said shell members having inwardly extending lip members which extend further toward the longitudinal central axis of said shell members than the end portions of the other of said shell members, and wherein said body housing means include a pair of elongated slots formed therein which are respectively engageable with said lip members of said shell member.
 14. An orthodontic biassing device according to claim 13 wherein said first and second elongated shell members are located one within the other, said inner shell member comprising a hollow member, and wherein the outer elongated shell member is of a springy material and includes said inwardly extending lip members.
 15. An orthodontic biassing device according to claim 14 further comprising a bar member secured to an end of said inner member and extending across said hollow opening.
 16. An orthodontic biassing device according to claim 15 wherein said body housing means includes an extension extending from an end thereof and adapted to engage under said bar member.
 17. An orthodontic biassing device according to claim 13 wherein said first and second elongated shell members are located one within the other, said outer shell member comprising a hollow member, and wherein said inner shell member is of a springy material which defines a hollow opening, said inner shell member including said inwardly extending lip members.
 18. An orthodontic biassing device according to claim 17 further comprising a bar member secured to an end of said outer member and extending across said hollow opening.
 19. An orthodontic biassing device according to claim 18 wherein said body housing means includes an extension extending from an end thereof and adapted to engage under said bar member.
 20. An orthodontic biassing device according to claim 17 wherein said outer shell member is embedded in acrylic, or the like.
 21. An orthodontic biassing device according to claim 1 comprising a bar member extending across an end of each of said elements, said bar member serving as an end stop for said body housing means inserted in said elements.
 22. An orthodontic biassing device according to claim 1 wherein said connecting means comprises at least one projection extending from said body housing means and at least one slot in said element, said projection engaging said slot for non-rotatably connecting said body housing means to its respective element.
 23. An orthodontic biassing device according to claim 1 wherein each of said elements includes a hollow member for receiving a body housing means and an openable cover coupled to said hollow member to provide an access opening for connecting and detaching a body housing means from its respective element.
 24. An orthodontic biassing device according to claim 23 wherein said cover includes a projection thereon and wherein said hollow member includes a groove therein which is adapted to receive said projection for locking said cover to said hollow member.
 25. An orthodontic biassing device according to claim 23 wherein said hollow member comprises a generally part-cylindrical member, and wherein said cover comprises a generally part-cylindrical member which is engageable with said hollow element to form a generally cylindrical member when said cover is closed.
 26. An orthodontic biassing device according to claim 23 wherein said cover has an opening therein so as to allow communication with a body housing means through said cover when said cover is closed.
 27. An orthodontic biassing device according to claim 25 wherein said cover is formed of a springy material and has at least one projection thereon, and wherein said hollow member includes a depression therein which is adapted to receive said at least one projection for locking said cover to said hollow member in the closed position.
 28. An orthodontic biassing device according to claim 23 wherein said cover is hingedly coupled to said hollow element.
 29. An orthodontic biassing device according to claim 28 wherein said hollow member includes means extending therefrom in the vicinity of an end thereof, and wherein said cover includes an opening engageable with said extending means for hingedly coupling said cover to said hollow member.
 30. An orthodontic biassing device according to claim 29 wherein said opening comprises a first entrance portion having a width which is smaller in dimension than the thickness of said projection, and a second opening portion interior of said entrance portion and which is dimensioned so as to loosely receive said projection.
 31. An orthodontic biassing device according to claim 23 wherein said hollow member is a generally part-cylindrical member and wherein said cover comprises a generally part-cylindrical member formed of a springy material and which comprises more than half a cylinder in cross-section, said cover being slideable about the periphery of said hollow member for selectively opening and closing said access opening.
 32. An orthodontic biassing device according to claim 31 wherein said cover has a projection thereon and wherein said hollow member includes a depression therein which is adapted to receive said projection for locking said cover to said hollow member in the closed state.
 33. An orthodontic biassing device according to claim 1 wherein each of said elements includes a hollow member including an access opening for receiving a Body housing means, and tab means extending from said hollow member which are foldable over an inserted body housing means for locking said body housing means into said hollow member.
 34. An orthodontic biassing device according to claim 33 wherein at least one of said hollow member and body housing means has a projection thereon, and wherein the other of said hollow member and body housing means has a depression therein engageable with said projection for locking said body housing means in said hollow member.
 35. An orthodontic biassing device according to claim 23 wherein said hollow member is generally rectangular, and wherein said cover includes means extending over a substantial portion of said hollow member and engageable with at least one edge of said generally rectangular hollow member.
 36. An orthodontic biassing device according to claim 23 wherein said cover has a through opening therein communicating with said body housing. 